
From  "Michael Blasnik" <michael.blasnik@verizon.net> 
To  <statalist@hsphsun2.harvard.edu> 
Subject  st: Re: Re: RE: Re: eliminate negative values and their positivecounterpart 
Date  Tue, 06 Mar 2007 17:17:25 0500 
Sorry, (my mistake) this line should be simply omitted. Both npos and nneg are defined later on.
I guess the solution proposed by Mr Blasnik will exclude observations if the sum
over a group is zero, but should it be a necessary condition?
30
30
30
(with all other variables being same)  e.g. bought apples for 30, than returned them to the cashier, than decided to buy them again :)
This should simplify to 30, but the sum over the group is not 0.
it is a pity that I can't do as I have written, i.e. count if after egen
Sincerely yours,
Sergiy Radyakin
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